I have a trane air handler 2 ton with electric heat and every time the heater kicks off it trips my breaker

An electrician might turn off power to the unit, remove Heat Strip from Contactor/Relay and look for resistance between the Element wiring and Ground.
If shorted, they will likely physically look for the short to ground.
A quick Story, I was working in an Attic several years ago and was getting shocked when I touched EMT, I first assumed a conduit had separated and with a short on that circuit, but with conduit separated it would become live instead of tripping the Breaker.
Tic Tracer Showed it was the Ductwork that was Live. Then turned off breakers until the voltage was gone. It was the Air Handler Breaker, Opening the Air Handler I found the Heat Element had Shorted to the Unit, but since the Unit had NO ground, the Unit became Live.
Remove the Short, hooked up a ground and all was OK.
Your Ground seems intact.